The degradation of the light chain of human plasminogen will be studied by chromatographic, gel sequencing and activity procedures to ascertain the relative stability of the free form as compared to the light chain when complexed with streptokinase (SK). Degradation products of SK will also be analyzed in an attempt to determine at a molecular level which residues of SK are required for the expression of plasminogen activator activity. The non-plasminogen protease activities in human blood will be isolated, characterized, and an attempt will be made to identify their biological function if an animal model can be found which shows these activities. These proteases do not appear to be involved in the blood coagulation or fibrinolysis systems.